Extract Vue frontend into separate container and add stp_wasm crate

Move Vue app from nginx/vue/ to top-level vue/ with its own Dockerfile,
update docker-compose configs and nginx proxy to serve from the new
container, and add initial Rust WASM crate (stp_wasm). Also fix .gitignore
to exclude Rust target/ directories.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nginx/nginx_dev.conf.template

@@ -28,9 +28,6 @@ http {
         listen 80;
         server_name $DOMAIN www.$DOMAIN;
 
-        root /etc/nginx/html;
-        index index.html;
-
         location /uploads/ {
             alias /uploads/;
             add_header X-Content-Type-Options nosniff always;
@@ -39,17 +36,11 @@ http {
         }
 
         location / {
-            try_files $uri $uri/ /index.html;
-        }
-
-        location = /robots.txt {
-            allow all;
-            log_not_found off;
-            access_log off;
-        }
-
-        location = /img/stamps/mine.gif {
-            add_header Access-Control-Allow-Origin *;
+            proxy_pass http://vue:5173;
+            proxy_http_version 1.1;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection "upgrade";
+            proxy_set_header Host $host;
         }
 
         location $BACKEND_ENDPOINT {